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Isocyanates - methodology for gas and particle generation, sampling and detection
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Isocyanates are mainly used in the industry for the production of polyurethane (PUR) plastics. Workers are at risk of being exposed during the manufacturing of PUR. During thermal degradation of PUR, isocyanates are released and workers involved in hot work such as fire-fighting, welding etc. may also be exposed.

Isocyanates are known to cause allergic diseases and are the most common cause of occupational asthma. Some of the isocyanates used are suspected human carcinogens. Exposure among workers occurs frequently.

Isocyanates are reactive unstable compounds that need to be converted to stabile derivatives immediately during sampling to avoid underestimation of the exposure. Di-n-ButylAmine (DBA) was used as derivatising reagent to form stable urea derivatives. The DBA derivatives were analysed using LC-MS/MS.

In this thesis a novel technology for the direct monitoring of isocyanates using a Proton Transfer Reaction Mass Spectrometry (PTR-MS) is presented. Advancement of technology for the generation of isocyanates in an environmental chamber, dry sampling, particle-size fractionated sampling and the testing of respirator filter cartridges are described.

The dry sampler was demonstrated to be robust and enabled sampling up to 32 h. Precise sampling without the need of field extraction was made possible.

The particle-size fractionated sampling efficiently separated gas-phase and respirable particle-borne isocyanates (< 4µm in diameter).

Two personal protective respirator filter cartridges were studied. No trend of impaired performance for mono-isocyanates throughout 48-h exposure tests was found.

The distribution patterns, in a steady-state tube-furnace oven, between gas phase and different particle-phase fractions of isocyanates produced in fires were investigated. The substantial degradation of a PVC-carpet containing PUR and a wood board with a MDI based binder resulted mainly in the formation of high levels of monoisocyanates.

Place, publisher, year, edition, pages
Stockholm: Department of Analytical Chemistry, Stockholm University , 2012. , 107 p.
Keyword [en]
Isocyanate, PUR, Dry sampler, PTR-MS, Transfer line, PPE, Environmental Chamber, Respirable Particles, Denuder Impactor, Aerosol, Particles, Impinger, air sampling, LC-MS, di-n-butylamine, DBA, ICA, MIC, HDI, TDI, IPDI, MDI, Occupational Exposure, Exposure, Occupational Health
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-79501ISBN: 978-91-7447-556-2 (print)OAI: oai:DiVA.org:su-79501DiVA: diva2:550206
Public defence
2012-10-05, Vita salen, Hässleholm Kulturhus, Vattugatan 18/Järnvägsgatan 23, Hässleholm, Hässleholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 2: Submitted. Paper 5: Accepted.

Available from: 2012-09-13 Created: 2012-09-04 Last updated: 2014-03-17Bibliographically approved
List of papers
1. Dry Sampling of Gas-Phase Isocyanates and Isocyanate Aerosols from Thermal Degradation of Polyurethane
Open this publication in new window or tab >>Dry Sampling of Gas-Phase Isocyanates and Isocyanate Aerosols from Thermal Degradation of Polyurethane
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2014 (English)In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 58, no 1, 28-49 p.Article in journal (Refereed) Published
Abstract [en]

The performance of a dry sampler, with an impregnated denuder in series with a glass fibre filter, using di-n-butylamine (DBA) for airborne isocyanates (200ml min−1) is investigated and compared with an impinger flask with a glass fibre filter in series (1 l min−1). An exposure chamber containing 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and 2,4- and 2,6-toluene diisocyanate (TDI) in the concentration range of 5–205 μg m−3 [0.7–33 p.p.b.; relative humidity (RH) 50%], generated by gas- and liquid-phase permeation, was used for the investigation. The precision for the dry sampling for five series with eight samplers were in the range of 2.0–6.1% with an average of 3.8%. During 120-min sampling (n = 4), no breakthrough was observed when analysing samplers in series. Sixty-four exposed samplers were analysed after storage for 0, 7, 14, and 21 days. No breakdown of isocyanate derivatives was observed. Twenty-eight samplers in groups of eight were collecting isocyanates during 0.5–32h. Virtually linear relationships were obtained with regard to sampling time and collected isocyanates with correlation coefficients in the range of 0.998–0.999 with the intercept close to the origin. Pre- or post-exposure to ambient air did not affect the result. Dry sampling (n = 48) with impinger-filter sampling (n = 48) of thermal decomposition product of polyurethane polymers, at RH 20, 40, 60, and 90%, was compared for 11 isocyanate compounds. The ratio between the different isocyanates collected with dry samplers and impinger-filter samplers was in the range of 0.80–1.14 for RH = 20%, 0.8–1.25 for RH = 40%, 0.76–1.4 for RH = 60%, and 0.72–3.7 for RH = 90%. Taking into account experimental errors, it seems clear that isocyanic acid DBA derivatives are found at higher levels in the dry samples compared with impinger-filter samplers at elevated humidity. The dry sampling using DBA as the reagent enables easy and robust sampling without the need of field extraction.

Keyword
airborne isocyanates, dibutylamine derivatives, dry sampling, liquid chromatography–mass spectrometry, thermal decomposition
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-78817 (URN)10.1093/annhyg/met046 (DOI)000330833300004 ()23960047 (PubMedID)
Note

AuthorCount: 6;

Funders:

Swedish government;  Stockholm University 

Available from: 2012-09-05 Created: 2012-08-13 Last updated: 2017-12-07Bibliographically approved
2. Sampling of Respirable Isocyanate Particles
Open this publication in new window or tab >>Sampling of Respirable Isocyanate Particles
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2014 (English)In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 58, no 3, 340-354 p.Article in journal (Refereed) Published
Abstract [en]

An advanced design of a denuder impactor (DI) sampler has been developed for characterization of possible airborne isocyanate exposure in different particle size fractions. The sampler is equipped with 12 different parallel denuder tubes, 4 impaction stages with the cut-off values (d50) of: 9.5, 4, 2.5 and 1 µm, and an end filter that collects particles < 1 µm. All collecting parts were impregnated with di-n-butylamine DBA as the reagent in a mixture with acetic acid. The performance of the DI sampler was studied on a standard atmosphere containing gas and particulate isocyanates. The isocyanate atmosphere was generated by liquid permeation of 2,4-, 2,6-Toluene Diisocyanate (TDI), 1,6-Hexamethylene Diisocyanate (HDI) and Isophorone Diisocyanate (IPDI). 4,4’-Methylene Diphenyl Diisocyanate (MDI) particles were generated by heating of technical MDI and condensing the mixture of gas and particle-borne MDI in an atmosphere containing mixed salt particles. The study was performed in a 0.85 m3 environmental chamber with stainless steel walls. With the advancement of the DI sampler it is now possible to collect isocyanate particle samples for up to 320min. The performance of the DI sampler is essentially unaffected by the humidity. The DI sampler and the ASSET™ EZ4-NCO sampler (Sigma-Aldrich/Supelco, Bellefonte, PA, USA) gave similar results. Sample losses within the DI sampler are low. In the environmental chamber it was observed that the particle distribution may be affected by the humidity and ageing. A scanning mobility particle sizer (SMPS) was used to separate a flow of selected fractions containing MDI particles from mixed MDI and salt particles. The particle-size distribution had a maximum at about 300nm, but later in the environmental chamber 1 µm dominated. The distribution was very different as compared to with only NaCl or MDI present. The biological relevance for studying isocyanate nano particles is significant as these have the possibility to reach the lower airways where allergic reactions may occur. SMPS and isocyanate air sampling can be used for the investigation of isocyanate nano particles.

Keyword
aerosol, air sampling, DBA, denuder, impactor, isocyanate, respirable
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-101552 (URN)10.1093/annhyg/met067 (DOI)000333046700007 ()
Available from: 2014-03-11 Created: 2014-03-11 Last updated: 2017-12-05Bibliographically approved
3. Determination of Gas Phase Isocyanates Using Proton Transfer Reaction Mass Spectrometry
Open this publication in new window or tab >>Determination of Gas Phase Isocyanates Using Proton Transfer Reaction Mass Spectrometry
2011 (English)In: Analytical Chemistry Letters, ISSN 2229-7928, Vol. 1, no 4, 261-271 p.Article in journal (Refereed) Published
Abstract [en]

We report the development of proton transfer reaction-mass spectrometry (PTR-MS) methodology for on-line monitoring, using a direct reading instrument, of several typical gas phase isocyanates, including isocyanic acid (ICA), ethyl isocyanate (EIC), phenyl isocyanate (PhI), hexamethylene diisocyanate (HDI) and toluene diisocyanate (TDI). In the study, ICA and MIC were generated by thermal degradation of urea and 1,3-dimethylurea, respectively, while the other isocyanates were generated by liquid and gas permeation techniques. Comparative, reference measurements were made by sampling isocyanate atmosphere using impinger flasks containing the reagent di-n-butyl amine (DBA) then determining the resulting DBA derivatives by liquid chromatography (LC)-MS/MS. Reproducible measurements were obtained, with a <10 % drift in PTR-MS responses during a 12 month period. Further, there were linear correlations (R2>0.99) between the data acquired by the PTR-MS technique and air sampling followed by LC-MS/MS for all tested isocyanates in the concentration range 2-100 ppb, with a PTR-MS detection limits in the low ppb range. For all isocyanates except EIC, BIC, HDI and IPDI, the protonated molecular ions were the most abundant ions in the PTR mass spectra. Overall, the results show that the developed method enables sensitive, time-resolved measurements of airborne isocyanates to be acquired over several weeks.

National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-79556 (URN)10.1080/22297928.2011.10648228 (DOI)
Available from: 2012-09-05 Created: 2012-09-05 Last updated: 2013-10-15Bibliographically approved
4. Adsorption Efficiency of Respirator Filter Cartridges for Isocyanates
Open this publication in new window or tab >>Adsorption Efficiency of Respirator Filter Cartridges for Isocyanates
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2010 (English)In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 54, no 4, 377-390 p.Article in journal (Refereed) Published
Abstract [en]

In some industries, the temperature and the humidity will vary greatly between different work places, such as outdoor work in arctic or tropical climates. There is therefore a need to test respirator filters at conditions that simulate conditions that are relevant for the industries that they are used in. Filter cartridges were exposed to controlled atmospheres of varying isocyanate concentration, air humidity, and temperature in an exposure chamber. For isocyanic acid (ICA) and methyl isocyanate (MIC), the exposure concentrations were between 100 and 200 p.p.b., monitored using a proton transfer reaction mass spectrometer. ICA and MIC were generated by continuous thermal degradation of urea and dimethylurea. The breakthrough was studied by collecting air samples at the outlet of the filter cartridges using impinger flasks or dry samplers with di-n-butylamine as derivatization reagent for isocyanates followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. For hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), the exposure concentrations were between 4 and 20 p.p.b. and were generated by wet membrane permeation. To reveal the profile of adsorption in different layers of the respirator filters, representative samples from each of the layers were hydrolyzed. The hydrolysis products hexamethylene diamine and isophorone diamine were determined after derivatization with pentafluoropropionic anhydride (PFPA) followed by LC-MS/MS analysis. The two filter types studied efficiently absorbed both ICA and MIC. There was no trend of impaired performance throughout 48-h exposure tests. Even when the filters were exposed to high concentrations (similar to 200 p.p.b.) of ICA and MIC for 96 h, the isocyanates were efficiently absorbed with only a limited breakthrough. The majority of the HDI and IPDI (> 90%) were absorbed in the top layers of the absorbant, but HDI and IPDI penetrated farther down into the respirator filters during 120 h of exposure as compared to 16 h exposure.

Keyword
generation test atmosphere, hexamethylene diisocyanate, isocyanic acid, isophorone diisocyanate, methyl isocyanate, PPE, PTR-MS, respirator testing
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-50304 (URN)10.1093/annhyg/meq008 (DOI)000278218200003 ()
Note

authorCount :10

Available from: 2010-12-22 Created: 2010-12-22 Last updated: 2017-12-11Bibliographically approved
5. Detailed study of distribution patterns of polycyclic aromatic hydrocarbons and isocyanates under different fire conditions
Open this publication in new window or tab >>Detailed study of distribution patterns of polycyclic aromatic hydrocarbons and isocyanates under different fire conditions
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2014 (English)In: Fire and Materials, ISSN 0308-0501, E-ISSN 1099-1018, Vol. 38, no 1, 125-144 p.Article in journal (Refereed) Published
Abstract [en]

This study has examined the distribution patterns between gas phase and particle phase of some chemical compounds produced in fires. It has also addressed the question of the distribution of individual particle-associated species between the different size-ranges of particles. The chemical compounds studied and discussed in this paper are polycyclic aromatic hydrocarbons (PAHs), and isocyanates. The steady-state tube furnace, ISO/TS 19700, was chosen as the physical fire model in order to study the production of particles from different types of fire exposure, that is, oxidative pyrolysis, well-ventilated flaming fires and under-ventilated flaming post-flashover fires. Two materials were chosen for investigation, a polyvinyl chloride (PVC) carpet and a wood board. The particle production from the two materials investigated varied concerning both the amounts produced and the particle size distributions. The analysis of PAHs showed that volatile PAHs were generally dominant. However, when the toxicity of the individual species was taken into account, the relative importance between volatile and particle-associated PAHs shifted the dominance to particle-bound PAH for both materials. The substantial degradation in the tests of the low polyurethane content of the PVC carpet, and the (4,4-methylenediphenyl diisocyanate)-based binder in the wood board resulted in no or very small amount of quantifiable diisocyanates.

Keyword
particles, aerosol, size distribution, PAH, isocyanates, ISO/TS 19700 steady-state tube furnace
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-100869 (URN)10.1002/fam.2173 (DOI)000329855700010 ()
Note

AuthorCount:5;

Available from: 2014-02-18 Created: 2014-02-17 Last updated: 2017-12-06Bibliographically approved

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